A future without nuclear energy has been on the drawing board for Southern California since a radiation leak shut down San Onofre in January 2012.

With the recent announcement of the facility’s permanent retirement, diverse architects of the state’s power grid are acting on those plans.

Utility executives last week resubmitted a previously spurned application for a major new natural-gas plant on the southern outskirts of San Diego, as engineers look to shore up power supplies across an area larger than the state of Maryland.

Any solutions will have to navigate increasing technological challenges and a complex landscape of environmental and clean-energy mandates in California.

The cost implications are unclear for ratepayers, who already are underwriting the state’s aggressive green-energy makeover. Utility engineers in San Diego County and the Los Angeles Basin are studying how to make up for San Onofre, which generated enough electricity to power 1.4 million homes.

Beyond producing power, San Onofre also provided crucial voltage support to the grid — helping Southern California import electricity to its coastline residents and businesses.

The state’s main grid operator said a series of transmission upgrades and new voltage support equipment, scheduled to come online this week in Huntington Beach, have ensured adequate power supplies for the summer — save for an extraordinary combination of hot weather and equipment failures.

In the meantime, battle lines are being drawn in response to San Diego Gas & Electric’s announcement that it wants to expand the region’s network of natural-gas plants. Advocates of alternatives to fossil fuels said resources should be focused first on conservation, more-efficient uses of electricity and greater reliance on renewable energy, including rooftop solar systems.

East of San Diego, a solar-energy building boom is underway as industrial-scale renewable energy plants fan out across thousands of acres in the Imperial Valley desert.

The first two projects in that category — a wind farm at Ocotillo and portions of a 900-acre solar plant beside the U.S.-Mexico border near Calexico — have tapped into the year-old Sunrise Powerlink transmission line that delivers power to SDG&E customers.

North and east of Los Angeles, even bigger transmission projects by Southern California Edison are clearing pathways for more renewable energy from the windy Tehachapi Mountains and the sun-drenched Antelope Valley and Mojave Desert.

In southern Orange and northern San Diego counties, where the San Onofre shutdown will be felt most heavily, new rooftop solar arrays have added about 50 megawatts of generation capacity to the grid during the past year. San Onofre once provided the same area with 440 megawatts of around-the-clock power.

Solid backups needed

SDG&E President Michael Niggli said renewable-energy production alone cannot replace nuclear energy, even when considering government mandates and incentives.

“Renewables are great, but they’re controlled by Mother Nature,” said Niggli, who announced the plan to resubmit an application for building the rapid-fire, or peaker, Pio Pico natural-gas plant in Otay Mesa. “So you need these solid backups like the (natural-gas) peakers.”

The California Public Utilities Commission had rejected the company’s Pio Pico proposal in March. It said the project, which would cost ratepayers more than $1 billion, was not needed until at least 2018.

But the panel said it would entertain an application refiling if certain circumstances changed.

Bill Powers, a San Diego-based engineer and consultant whose calculations helped defeat the first Pio Pico application, said the pursuit of new natural-gas generators runs counter to energy-consumption trends.

“What I assert — and what utilities around the country contend and utility executives say in their own forums — is that we’re seeing a paradigm shift,” Powers said. “We’re seeing lower consumption per capita, and we’re seeing a transition in California to self-generated power, especially rooftop power.”

Yet personal energy habits remain in flux.

The California Independent System Operator anticipates a 2.3 percent uptick in electricity demand this summer associated with ongoing economic recovery, citing an analysis by Moody’s Analytics.

Plug-in vehicles, were they to truly catch on, would dramatically increase per-capita electricity consumption — with major implications for power generation and delivery systems.

Natural-gas solution?

Energy markets and environmental regulations stand in the way of simple solutions for ensuring a stable, sufficient power supply for Southern California.

Rock-bottom prices for natural gas, a consequence of the boom in U.S. exploration and extraction, do not translate directly into savings at plants like Pio Pico — whose value and billing are based on peak-generating capacity instead of actual energy produced.

California’s clean-air and clean-energy laws treat new fossil-fuel plants as a last resort, to be called on after conservation, efficiency and renewable-energy options have been exhausted. And highly populated areas consistently shun new power plants.

“You’ve got all those geopolitical reasons why it’s very difficult to put a plant near the population,” said Chuck Adamson, manager of major transmission projects for Southern California Edison.

He said Edison is still evaluating the effects of the San Onofre shutdown, including whether additional transmission and generation upgrades might be required.

“Our conclusions won’t be out for some months,” Adamson said. “At a sort of high level, the big thing is that the power (from San Onofre) has to be replaced.”

SDG&E said it has been compelled to pursue new natural-gas generators as the state phases out power plants that use the ocean for a process called once-through cooling, which environmentalists criticize because it harms marine life.

The retirement of San Onofre and the South Bay Power Plant in Chula Vista — reduced to rubble in a demolition in February — leaves just one facility in San Diego County with once-through-cooling: the Encina Power Station in Carlsbad, owned by New Jersey-based NRG Energy.

SDG&E turned down an NRG bid to build a modern successor plant on adjacent property, saying the project would be too expensive.

With or without a Carlsbad facility, Niggli of SDG&E described new natural-gas generation as a necessary component of meeting the region’s electricity demands — a conclusion vigorously contested by some consumer and green-energy advocates.